Fix unread message conversation separator for dark theme

Fixes #6265
// FREEBIE

res/drawable/last_seen_divider_text_background.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" >
-    <solid android:color="@color/white"/>
+    <solid android:color="?conversation_item_last_seen_text_background"/>
 
     <corners android:radius="65dp"/>
     <padding android:bottom="15dp" android:left="15dp" android:right="15dp" android:top="15dp"/>

res/layout/conversation_item_last_seen.xml

@@ -6,7 +6,7 @@
              android:paddingTop="10dp"
              android:paddingBottom="10dp"
              android:layout_marginBottom="5dp"
-             android:background="@drawable/last_seen_background">
+             android:background="?conversation_item_last_seen_background">
 
         <TextView android:id="@+id/text"
                   android:layout_width="wrap_content"

res/values/attrs.xml

@@ -72,6 +72,8 @@
     <attr name="conversation_item_sent_text_indicator_tab_color" format="reference|color"/>
     <attr name="conversation_item_sent_indicator_text_background" format="reference" />
     <attr name="conversation_item_header_background" format="reference"/>
+    <attr name="conversation_item_last_seen_background" format="reference|color"/>
+    <attr name="conversation_item_last_seen_text_background" format="color"/>
 
     <attr name="dialog_info_icon" format="reference" />
     <attr name="dialog_alert_icon" format="reference" />

res/values/themes.xml

@@ -157,6 +157,8 @@
         <item name="conversation_item_received_text_primary_color">@color/white</item>
         <item name="conversation_item_received_text_secondary_color">#BFffffff</item>
         <item name="conversation_item_header_background">@drawable/conversation_item_header_background</item>
+        <item name="conversation_item_last_seen_background">@drawable/last_seen_background</item>
+        <item name="conversation_item_last_seen_text_background">@color/white</item>
 
         <item name="quick_camera_icon">@drawable/quick_camera_light</item>
         <item name="quick_mic_icon">@drawable/ic_mic_grey600_24dp</item>
@@ -244,6 +246,8 @@
         <item name="conversation_item_received_text_secondary_color">#BFffffff</item>
         <item name="conversation_item_sent_indicator_text_background">@drawable/conversation_item_sent_indicator_text_shape_dark</item>
         <item name="conversation_item_header_background">@drawable/conversation_item_header_background_dark</item>
+        <item name="conversation_item_last_seen_background">#66333333</item>
+        <item name="conversation_item_last_seen_text_background">#ff333333</item>
 
         <item name="verification_background">#ff333333</item>